Have done a clean install of 102.0.4880.51 and all seems to be working OK now. Just have to set it all up again.

There is something odd going on, I tried the update and it seemed to install OK but at the end when I clicked 'relanuch now' it went back to the same page saying "Your version is 102.0.4880.46" and "Restart Opera to update to version 102.0.4880.51" and it seems to be stuck in that loop now. So I haven't tried any of your suggestion's yet.
It seems to be looking like a clean install might be needed.
I then found I couldn't submit this reply from opera and had to do it from ms edge.

C:\Net\Opera\opera.exe - regular Opera.
Either would be OK but perhaps 'all users' might be best.
Have just tried changing the double back slashes to a single in the superuser reg file but no difference.

I had a couple of try's at altering the reg file in https://superuser.com/questions/1328499/how-to-make-a-portable-version-of-opera-the-default-browser but kept getting "cannot import ... some processes open or not have privileges", made sure Opera was shut down and ran as admin etc., but no difference that is the one that stops vivaldi portable being default.

Thanks but I already tried that and couldn't get it to work and whatever it did also stopped vivaldi portable as being default so had to reinstall that. I don't see why Opera developers couldn't give the option if other chrome based browsers can do it.

I have read one post on how to set Opera portable as Windows default browser on the forum and others off the internet but none work for me and I wondered if anyone knows why it cannot be set as default because other portable versions of browsers can, such as 'Vivaldi' and 'Slimjet' , both of which I believe are chrome based, and various others.
I would switch to Vivaldi full-time but Opera has a couple of features I like that can't seem to be implemented in other browsers
I have tried using symlinks to stop the install version of scattering files all over my PC but it is a bit of a pain to maintain, particularly if I allow updates.

Have done a clean install of 102.0.4880.51 and all seems to be working OK now. Just have to set it all up again.

There is something odd going on, I tried the update and it seemed to install OK but at the end when I clicked 'relanuch now' it went back to the same page saying "Your version is 102.0.4880.46" and "Restart Opera to update to version 102.0.4880.51" and it seems to be stuck in that loop now. So I haven't tried any of your suggestion's yet.
It seems to be looking like a clean install might be needed.
I then found I couldn't submit this reply from opera and had to do it from ms edge.

Opera stopped opening links from external sources such as in emails since it updated to 'Opera One(version: 102.0.4880.46)'.
I have tried disabling extensions etc. I did set edge to be default browser and it opens links in emails but if i reset opera to be default browser nothing happens.
I have resisted a reinstall so far as find the opera sync never works very well and it takes me ages to get it running properly again.

Sort-of found a fix, resetting the passphrase and sync did not do anything, it was still displaying the wrong one all the time so uninstalled and reinstalled but now it is syncing and not asking for a passphrase, my normal opera log-in seems to be all that is required.

No, it said it was the wrong passphrase but it will not let me correct it or delete it. I am not sure if something else caused it as the only difference is that the first letter is capitalised and I don't believe i did that, I am wondering if it is some of the win 11 autocorrect stuff that might have done it.

I was having a look at opera one and entered one character wrong in the passphrase for sync and it won't let me change it.
Even after shutting opera down and restarting the incorrect passphrase is still in the box, how do I edit or delete it so I can enter the correct one?